Secondary musculoskeletal complications following paralysis cause increased human suffering, impaired quality of life, and extended health care costs to society. Skeletal muscle becomes highly fatigable after spinal cord injury, which limits its functional use for standing, grasping, or ambulating with electrical stimulation. Associated with muscle fatigue is a severe loss of bone density. The long term objective of this project is to establish exercise guidelines for individuals with paralysis to prevent the secondary changes to the musculoskeletal system. This project will describe the musculoskeletal changes after paralysis, test a method to actively load the musculoskeletal system acutely, and establish if the method is effective at preventing or reversing the musculoskeletal changes after paralysis. The specific aims of the project are to: 1) determine if chronically paralyzed muscle can produce higher torques for longer times by stimulating the muscle under adaptive feedback control when compared to constant frequency open loop stimulation; 2) determine the physiological properties of the soleus muscle from both lower extremities in individuals with acute and chronic paralysis before, during, and after 6 months of training the unilateral soleus muscle; 3) determine the bone mineral density of the tibia and femur in both lower extremities of individuals with acute and chromic paralysis before, during, and after 6 months of exercising the unilateral soleus muscle. This project will provide empirical evidence about the plasticity of the musculoskeletal system after paralysis. The benefits of this newly developed adaptive feedback controlled exercise may provide a standard that individuals with paralysis may use in an effort to maintain their musculoskeletal properties following paralysis.